National Repository of Grey Literature 8 records found  Search took 0.01 seconds. 
Electron back-scattered diffraction as a method for grain boundary analysis in polycrystalline materials
Malachov, Martin ; Jäger, Aleš
Current development of analytical techniques in scanning electron microscopy allowed us to obtain precise information about the crystallography and chemical composition of materials. Aim of this work is to explain electron back-scatter diffraction (EBSD) technique and its utilization in grain characterization of polycrystalline materials.
Annealing of thin film polycrystalline silicon solar cells in water vapour
Pikna, Peter ; Fejfar, Antonín
Samples of thin film polycrystalline silicon solar cells prepared by the Company CSG Solar AG were treated in water vapour. Appearance of treated solar cells was very similar to samples etched in a solution of acids, which is commonly used to approach the bottom part of pn junction. No significant improvement of measured open-circuit voltage Voc was observed, but the etching effect of water vapour can determine the upper limit of temperature, pressure and treatment time for water vapour passivation. Novel approach for preparation of a depth profile to approach the bottom part of pn junction is proposed.
Study of Influence of Segregated Impurities on Magnetism of Grain Boundaries and Free Surfaces in FCC Nickel and Cobalt
Všianská, Monika ; Vémolová, H. ; Šob, Mojmír
We present an ab initio study of segregation of 12 nonmagnetic sp impurities (Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb and Te) at the Sigma5(210) grain boundary (GB) and (210) free surface (FS) in ferromagnetic fcc nickel and cobalt. We analyze their effect on structure, magnetic and mechanical properties. We determine the preferred segregation sites of the impurity atoms, their segregation enthalpies and strengthening/embrittling energies with their decomposition into the chemical and mechanical components. In this contribution, we focused on the influence of segregated impurities on the magnetic moments of neighbouring atoms, the changes in the density of states and why the magnetically dead layers may be present in nickel but not in the cobalt.
Effect of segregated nonmagnetic sp-impurities on the properties of grain boundaries and surfaces in nickel
Všianská, Monika ; Šob, Mojmír
We present an ab initio study of segregation of 12 nonmagnetic sp impurities (Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb and Te) at the Sigma5(210) grain boundary (GB) and (210) free surface (FS) in fcc ferromagnetic nickel and analyze their effect on structure, magnetic and mechanical properties. We determine the preferred segregation sites of the impurity atoms, their segregation enthalpies and strengthening/embrittling energies with their decomposition into the chemical and mechanical components. We find that the value of mechanical component is dependent on the type of the stable segregation position and is nearly constant in each period. On the other hand the chemical component changes strongly within each period and is determined by the electronegativity of impurity atoms. Magnetically dead layers found at the impurity segregated GB and FS are caused by a strong hybridization of sp states of the impurities with the d states of nickel.
Structure and magnetism of clean and impurity-decorated grain boundaries in nickel from first principles
Všianská, Monika ; Šob, Mojmír
We present a detailed theoretical study of segregation of sp-elements from the 3rd-5th period (Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb and Te) at the Sigma5(210) grain boundary (GB) in fcc FM Ni. Whereas there is a slight enhancement of magnetization at the clean GB and FS with respect to bulk nickel (3–7% and 24%, respectively), the studied impurities entirely kill or strongly reduce ferromagnetism at the GB so that magnetically dead layers are formed. We determine the preferred segregation sites at the GB for the impurities studied, their segregation enthalpies and strengthening/embrittling energies. We find interstitially segregated Si and P and substitutionally segregated Al as a GB cohesion enhancer, and interstitially segregated S, Ge, As, Se and substitutionally segregated Ga, In, Sn, Sb and Te as GB embrittlers in Ni. As there is very little experimental information on GB segregation in nickel most of the present results are theoretical predictions which may motivate future experimental work.
Control of intergranular oxidation by thermal treatment
Rothová, Věra ; Buršík, Jiří ; Svoboda, Milan
The effect of pre-annealing at 800 °C in argon atmosphere on high temperature corrosion at 1050 °C in air was studied on two high purity nickel grades and compared to a commercial purity nickel. Moreover, the influence of fabrication was analyzed in the case of cast and cold-rolled Puratronic® nickel samples. The mutual grain orientation was measured by means of electron backscatter diffraction and grain boundaries were characterized in terms of the coincidence site lattice model. The scanning electron microscope characterization of cross sections of all the oxidized samples has been performed and compared with the literature. The influence of purity and fabrication on the high temperature oxygen ingress in nickel was discussed in terms of grain boundary character distribution.
Nukleace dislokací v hranici mezi zrny během deformace
Gemperle, Antonín ; Gemperlová, Juliana ; Gärtnerová, Viera
New mechanism of slip transfer across grain boundary was discovered. Slip dislocations accumulate in the boundary and create important internal stresses that nucleate a set of close parallel sources. These emit dislocations into the undeformed grain.
Grain boundary magnetism - ab initio study
Čák, Miroslav ; Šob, Mojmír ; Hafner, J.
We study the magnetic structure of the symmetrical tilt grain boundary sigma 5 (310) in iron. It is shown, that local magnetic moments of atoms at grain boundary is enhanced when compared to the bulk value. This is interpreted as a magnetovolume effect.

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